You have a week with days and you want to iterate over the week and never met nil, but:

week = [:mon, :tue, :wed, :thu, :fri, :sat, :sun]
week[0] # => :mon
week[3] # => :thu
week[6] # => :sun
week[7] # => nil... stop what?! I need monday!

But it's possible with CircularArray

require 'circular_array'

circular_week = CircularArray[:mon, :tue, :wed, :thu, :fri, :sat, :sun]

# It behaves like Array. Basically it inherits Array:
circular_week.kind_of? Array # => true

# But it is endless:
circular_week[0] # => :mon
circular_week[3] # => :thu
circular_week[6] # => :sun
circular_week[7] # => :mon
circular_week[8] # => :tue
circular_week[9] # => :wed
circular_week[10] # => :thu
circular_week[11] # => :fri
circular_week[12] # => :sat
circular_week[13] # => :sun
circular_week[14] # => :mon
# great!

You can use it for recursive matching, but do not forget to add anti-infinity loop clause

Only for empty collection in returns nil

empty_circular_array = CircularArray.new([])
empty_circular_array[1] # => nil

1. Round-robin selection algorithm
2. Matching over a list of possible solutions
3. Cycling dates for complex delivery logic

Add this line to your application's Gemfile:

gem 'circular_array'

And then execute:

$ bundle

Or install it yourself as:

$ gem install circular_array

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/[USERNAME]/circular_array. This project is intended to be a safe, welcoming space for collaboration, and contributors are expected to adhere to the Contributor Covenant code of conduct.

The gem is available as open source under the terms of the MIT License.

Everyone interacting in the CircularArray project’s codebases, issue trackers, chat rooms and mailing lists is expected to follow the code of conduct.